James Comey became FBI director last year, at a time when Osama bin Laden was dead, terrorism at home was on the decline and the United States was shrinking its inflammatory presence in the Muslim world. So naturally, he says the danger is way worse than you think.

Referring to al-Qaida groups in Africa and the Middle East, he recently told The New York Times, "I didn't have anywhere near the appreciation I got after I came into this job just how virulent those affiliates had become. There are both many more than I appreciated, and they are stronger than I appreciated."

It may look like we've greatly diminished if not eliminated the danger of Islamic extremism against American targets. In fact, Comey assures us, "that threat has metastasized." Of course cancer is far more deadly once it spreads.

In this respect he resembles just about every bureaucrat in the history of government. He thinks that his agency is vitally important and growing more so every day. If there had been a Federal Bureau of Stagecoaches when passenger trains and cars came along, it would still be in business and finding ways to justify its preservation and expansion.

Terrorism has fed the FBI's growth. Between 2001 and 2013, its budget nearly doubled after adjusting for inflation. But Comey was not pleased on arriving to learn that he would be inconvenienced by last year's federal budget sequester.

"I was very surprised to learn how severe the potential cut is," he complained. He warned he might have to cut 3,000 jobs. His estimate was inflated -- the agency now says it eliminated just 2,200 positions through attrition. The agency's website, however, says it has 35,344 employees -- up by 30 percent since 2001.

Comey is upholding the tradition that once the government identifies an evil, the evil never goes away -- it only gets bigger and tougher, requiring ever-increasing efforts to combat it. The Department of Energy was created during the "energy crisis" of the 1970s. The crisis didn't last, but the department did.

The same pattern holds here. In the decade after 9/11, the number of terrorist episodes in this country averaged 17 a year, compared to 41 a year in the 1990s. Nor is al-Qaida gaining ground. Since 9/11, reports the National Consortium for the Study of Terrorism and Responses to Terrorism at the University of Maryland, it has carried out no attacks in the U.S.

But progress is never taken as progress. It's always interpreted as the calm before the storm.

When Comey arrived, nerves were raw from the Boston Marathon bombing, which sparked fears of a wave of domestic attacks. Since then, there has not been a single death from homegrown terrorism in the U.S. In the following 12 months, the number of Muslim-Americans arrested on terrorism charges was 15, below the annual average of 20.

"Almost all of these arrests were for attempting to join a foreign terrorist organization abroad, not for planning attacks in the homeland, and were motivated by sympathies with rebels in Syria and elsewhere rather than by al-Qaida's call for Muslims to attack the West," wrote David Schanzer of Duke University and Charles Kurzman of the University of North Carolina Chapel Hill in The News and Observer of Raleigh.

None of this matters to Comey or his associates in the federal government, which has an unbreakable addiction to dire forecasts. When it comes to national security, they see every silver lining as attached not just to a cloud, but to a skyful of black thunderheads.

In 1993, following the collapse of the Soviet Union, a nuclear-armed existential threat, the nominee to head the Central Intelligence Agency, James Woolsey, told the Senate Intelligence Committee, "Yes, we have slain a large dragon. But we live now in a jungle filled with a bewildering variety of poisonous snakes." The number of serious security threats, Woolsey claimed, had "grown, not shrunk."

This testimony came at a time of budget austerity. "His strong warnings about the gravity of threats appeared intended to serve notice that he would be highly wary of budget-cutting efforts that might weaken intelligence programs," reported The New York Times.

That's the logic of people in government. What begins as a legitimate concern becomes an irrational obsession. What begins as a temporary problem becomes a never-ending emergency.